Along Le Moutonnière, which connects the centre of Algiers with the suburb of El Harrach to the west, and all along the recently refurbished seafront at Les Sablettes, thousands of newly planted palm trees stand to attention. Hundreds more have been planted to the east of the capital, all along the motorway and the main roads, transforming what used to be known as "white" Algiers into a huge palm grove.

As the 17 April presidential elections draw near, the trees were meant to provide a showcase for the regime's longevity and the renovation of north Africa's largest city. In short an additional argument for the election campaign, launched last month.

Unfortunately, it fell flat.

The four-metre tall trees, which had to be planted with cranes, have become the butt of countless jokes. The daily newspaper Liberté wondered if such gigantic palms were suited to the local landscape and architecture, while the news website Tout sur l'Algérie exclaimed, "The wilaya [administrative region] has spent a fortune planting palm trees in the middle of the fast lane". The priorities, it continued, should be elsewhere with "the garbage piling up and potholed roads impassable in most neighbourhoods".

One driver posted a photo on the internet of a palm tree bent right across the road in a downpour, leading to scathing comments about "fly-away decor" and the potential danger of the trees.

No one seems to remember the origin of the project, which was to plant exactly 1.5m palm trees across the country to represent the official figure of 1.5 million chouhadas or martyrs who died in the Algerian war of independence – a figure contested by some historians.

However, the project was launched hastily in early 2012 and wasn't completed in time for the 50th anniversary independence celebrations that July. Nevertheless, it carried on, the aim being to show Algeria as green and radiant and to symbolise a country finally at peace. The reconciliation of Algerians traumatised by a decade of civil war was, of course, to be credited to the outgoing president, the best achievement of his term in office.

Abdelaziz Bouteflika has been in office since 1999 and is seeking a fourth mandate even though he is debilitated by illness. But the secrecy surrounding "operation palm trees" has triggered many bemused comments. Suspicions have been raised about a lucrative Spanish purchasing contract, even though palms are native to Algeria. Algerians, whose daily papers are filled with corruption tales, see proof of the Spanish connection in the type of protective covering used to protect the newly planted palms.

Investigating the claim is another matter. One journalist making inquiries at the police headquarters was politely shown the door – but only after her ID and accreditation were photocopied and neatly filed. "We'll call you back," she was told.

The project managers refer journalists to the Wali [governor], who refuses to talk to them.

Palm tree growers are evasive, with the exception of 37-year-old Kamel Béchir, whose family has been "in the palm tree business from father to son". He manages a 450-tree estate in El Hadjeb, near Biskra, a paradise for the Phoenix dactylifera, or Algerian date palm. Located some 400km south-east of Algiers, Biskra is also Algeria's market garden, and the cradle of the Deglet Nour, the world-famous Algerian date, recently upstaged by its Tunisian cousin.

A farmer collects dates from palm trees at a plantation in Ouargla, Algeria. Photograph: Louafi Larbi/Reuters

"Many of the palm trees in Algiers come from Biskra, and they are still getting them from here, but most aren't date palms," said Béchir. He wouldn't dream of allowing one of his precious trees to end up being asphyxiated by the side of a road. "I haven't sold any to Algiers; palm trees are sacred for me," he added.

Even non date-producing palms are invaluable in providing shade for market gardens. Palm trees have a gender and the male trees pollinate the female ones to produce the dates. In the past the wind took care of that, but now artificial pollination occurs by cloning or in vitro cultivation. One male plant can pollinate up to 100 female ones.

A laboratory at the Houari-Boumediene University of Science and Technology in Algiers bears witness to the importance of the palm tree in Algeria's social, cultural and economic life. The research director, Nadia Bouguedoura, has a huge board in front of her office on which every variety is recorded. She has published many scientific studies on the date palm and has devoted 18 years of her life to the subject.

There are 18m palm trees in Algeria now (compared with 6 million at independence).

They are spread over some 169,380 hectares at the foot of the Monts des Zibans in the east, along Oued Souf and Oued Rhir in the M'zab valley in the centre, and near the Timimoun salt lake in the south-west. In areas such as the M'zab Valley in the Ghardaïa wilaya or province (currently the scene of ethnic conflict between Arabs and Berbers), vital water distribution to farmers is still carried out according to the number of palm trees owned, or else shared out to families according to an ingenious date stone accounting system.

Palm trees are a source of national wealth and provide a livelihood for 83,000 farmers in Algeria. About 55% of the country's 18m palm trees produce dates, in particular the Deglet Nour, which earned $ 27.6m in exports last year, a micro-resource compared with oil and gas, which accounts for 90% of Algeria's export earnings, but one Algerians are very proud of.

The nation's palm trees, rather like its citizens, were neglected during the years of armed struggle against the Islamists. "That black decade cost us a great deal in economic terms and we lost 10 years of research," deplored Bouguedoura. "That was when the Tunisians overtook us."

So will there be a north African battle for the "religious fruit", as dates are sometimes called, being very popular during Ramadan. Algeria is trying to register a Deglet Nour label and Bouguedoura has taken on the task of protecting it. Unfortunately, a viral attack in western Algeria, which began at the end of the 19th century, led to a transportation ban for certain palm trees as well as their by-products, which include hats, coffins and baskets. French and Italian palm trees were excluded from Bouteflika's palm tree project in the capital, on claims they were infected with disease-bearing weevils. The origin of Algiers's new palm trees is such a closely guarded secret that even the experts don't know.

This summer the new trees may provide some shade for families picnicking by the sea, and respite from the heat for cars stuck in the city's monstrous traffic jams, not to mention the police roadblocks, even though the state of emergency was lifted in 2011. But their cost, as well as their origin, will remain shrouded in secrecy.

This article appeared in Guardian Weekly, which incorporates material from Le Monde